1. Filed of the Invention
The present invention relates to metal precursors useful for chemical vapor deposition (CVD) of high dielectric constant (κ) and/or ferroelectric metal oxide thin films.
2. Description of the Related Art
Zirconium and hafnium-containing silicates possess dielectric constant (κ) values in the range of from about 10 to 20, and therefore are highly useful as gate dielectric materials in various microelectronic structures and devices. Zirconium- and hafnium-containing ferroelectric or high dielectric constant complex metal oxides, such as Pb(Zr,Ti)O3 or (Ba,Sr)(Zr,Ti)O3, are also being considered for the manufacturing of microelectronic devices. For these latter applications dielectric constants in excess of 50 and, for ferroelectric materials, hysteresis polarization, are the properties that make these materials desirable.
In such applications, the choice of zirconium or hafnium source reagents is of critical importance for the successful chemical vapor deposition of high quality Zr/Hf-doped gate dielectric ferroelectric, or high dielectric constant metal oxide thin films.
Fabrication of high quality Zr/Hf doped gate dielectric, high dielectric constant and/or ferroelectric metal oxide thin films requires that the zirconium or hafnium CVD source reagents so employed produce a clean interface between the substrate surface and the Zr/Hf thin films deposited thereon. Deleterious occurrence of side reactions, e.g., when the substrate is silicon, produce predominantly silicon dioxide (SiO2), locally doped SiO2, and /or other surface impurities, are desirably minimized, because formation of such surface impurities reduces the capacitance and therefore compromises performance of the deposited gate dielectric, high dielectric constant and/or ferroelectric metal oxide thin films.
Further, the Zr/Hf source reagents must be thermally stable to avoid premature decomposition of such source reagents before they reach the CVD reaction chamber during the CVD process. Premature decomposition of source reagents not only results in undesirable accumulation of side products that will clog fluid flow conduits of the CVD apparatus, but also causes undesirable variations in composition of the deposited gate dielectric, high dielectric constant and/or ferroelectric metal oxide thin film.
Moreover, the Zr/Hf source reagents have to be chemically compatible with other source reagents used in the CVD process. “Chemically compatible” means that the Zr/Hf source reagents will not undergo undesirable side reactions with other source reagents, e.g., reagents containing silicon or other metals, such as Pb and/or Ti.
Finally, the Zr/Hf source reagents must be able to maintain their chemical identity over time when dissolved or suspended in organic solvents. Any change in chemical identity of source reagents in the solvent medium is deleterious since it impairs the ability of the CVD process to achieve repeatable delivery and film growth.
There is a continuing need in the art to provide improved Zr/Hf source reagents suitable for high efficiency CVD processes, for fabricating corresponding high quality Zr/Hf-doped gate dielectric, high dielectric constant and/or ferroelectric metal oxide thin films.